Should my diet change season to season?

It can. It is now more evident that eating organic seasonal plants and vegetables contains more bioavailable vitamins and minerals and is more beneficial than non seasonal food. Eating based on your ancestoral food is also beneficial if you live in a different country than your ancestors .
Change seasons. Yes. There are many factors. One factor is the availability of the foods in your diet e.g. Fruits are plentiful in the summer and harder to buy in the winter. Ones calorie requires may vary by the season as usually people are more physically active in the summer as opposed to winter.